Brushless DC motors in various forms are well known in the art as described, for example, in U.S. Pat. Nos. 4,228,384 and 6,307,337. Such motors use an electronic controller instead of an armature commutator and brush assembly to switch the flow of current to individual motor winding coils.
A major limiting factor in the performance of conventional DC motors is internal heating, where the heat generated in the iron-cored coils of the motor armature escapes via an inefficient thermal path through the shaft and bearings of the motor assembly or through the airgap between the armature and field magnets to an outer casing.
In a brushless DC motor, the motor armature is a permanent magnet rotor assembly and the stator comprises a group of wound iron core coils. For better cooling, the stator coils are positioned in a casing to provide a short, efficient, thermal path to the outside air. Cooling can further be improved by blowing air over the casing and adding heat-removing fins. This ease of cooling allows a brushless motor to produce a much higher power in relation to its size than a motor with a conventional brush and commutator assembly.
A major advantage of brushless motors is their lack of conventional commutator and brush hardware. These items are a source of wear and may require frequent maintenance.
Brushless motors have certain disadvantages. For example, in order to drive a brushless motor, control electronics are necessary to selectively switch current through appropriate motor winding coils. The circuitry is often complex in order to provide the necessary timing sequence. In addition, the use of wound iron-core coils increases the weight and size of the motor assembly. Further, eddy current losses produced in iron-core coils reduce motor efficiency. These factors increase the manufacturing cost of devices using brushless motor technology.
Typically, a drive motor is connected to another assembly to perform a useful function. A motor, for example, may be connected to a fan, pump, or other type of device to provide operating power for the device.
Integrated assemblies can be made, however, using brushless drive motor technology, where the functional components of a powered device are an integral part of the motor assembly.
Accordingly, a need exists for an improved integrated brushless direct current motor device that does not use iron core coils, is easily cooled, and is compact and economical to manufacture.